structure5
Class ReverseComparator<E extends java.lang.Comparable<E>>

java.lang.Object
  structure5.ReverseComparator<E>

All Implemented Interfaces:

java.util.Comparator<E>

public class ReverseComparator<E extends java.lang.Comparable<E>>
extends java.lang.Object
implements java.util.Comparator<E>

Implementation of the Comparator interface that provides a Comparator.compare(Object,Object) method that compares two objects using those objects default compareTo methods. Reverse comparator however, reverses the natural comparison as follows:

Were we to call compare(a,b), ReverseComparator would return the following:

     >0 if a < b
      0 if a = b
     <0 if a > b
 

Example usage:

To print out the equality relationship between two randomly generated integers we could use the following:

 public static void main(String[] argv){
     Random  rand = new Random();
     Comparator c = new ReverseComparator();
      
     //generate two random Integers
     Integer a = new Integer(rand.nextInt(100));
     Integer b = new Integer(rand.nextInt(100));
      
     //print out the proper equality relationship between these integers
     if(c.compare(a,b) > 0) System.out.println("A:" + a + " > B:" + b);
     else if (c.compare(a,b) < 0) System.out.println("A:" + a + " < B:" + b);
     else System.out.println("A:" + a + " = B:" + b);
 

 

Field Summary

protected java.util.Comparator<E>

base

Constructor Summary

ReverseComparator()
Construct a comparator that generates reverse natural comparison

ReverseComparator(java.util.Comparator<E> base)
Construct a comparator that generates reverse of another comparator

Method Summary

int	compare(E a, E b) Compare two values, a and b.
boolean	equals(java.lang.Object b) Returns true if the other object is a NaturalComparator.

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

base

protected java.util.Comparator<E extends java.lang.Comparable<E>> base

Constructor Detail

ReverseComparator

public ReverseComparator()

Construct a comparator that generates reverse natural comparison

Postcondition:

constructs a comparator that orders in reverse order

ReverseComparator

public ReverseComparator(java.util.Comparator<E> base)

Construct a comparator that generates reverse of another comparator

Parameters:

base - the ordering to be reversed

Postcondition:

constructs a Comparator that orders in reverse order of base

Method Detail

compare

public int compare(E a,
                   E b)

Compare two values, a and b. Simply calls the default compareTo method for a on b.

Specified by:

compare in interface java.util.Comparator<E extends java.lang.Comparable<E>>

Parameters:

a - object performing the compare

b - the object being compared

Returns:

value <, ==, > 0 if a <, ==, > b using a.compareTo

Precondition:

a, b non-null, and b is of type of a

Postcondition:

returns value <, ==, > 0 if a <, ==, > b

equals

public boolean equals(java.lang.Object b)

Returns true if the other object is a NaturalComparator.

Specified by:

equals in interface java.util.Comparator<E extends java.lang.Comparable<E>>

Overrides:

equals in class java.lang.Object

Parameters:

b - a possible NaturalComparator

Returns:

true if b is a NaturalComparator

Postcondition:

returns true if b is a NaturalComparator